Silencer



Aug; 2, 1927. 1,637,385 I H. P. MAXIM SILENCER Filed Jan. 25. 1923 2 Sheets-Sheet 1 INVENTOR ATTORNEYS Aug. 1927. H. P. MAXIM 1,637,385

SILENCER Filed Jan. 25. 1923 2 Sheets-Sheet 2 F INVENTOR fl l a 7 I ATTORNEYS Patented Aug. 2, 1927.

UNITED STATES PATENT OFFICE.

HIRAM PERCY MAXIM, 0F HARTFORD, CONNECTICUT, ASSIGNOR TO THE HAITI SILENCEB COMPANY, OI HARTFORD, NECTIGU'I'.

CONNECTICUT, A CORPORATION 01 CON- SILENCER.

Application filed January 25, 1923. Serial No. 615,484.

The subject of this application for Letters Patentis a silencer for quieting the noises of explosive engines, blowers, air compressors and the like and more particularly the objectof the invention is the design of a silencer for employing certain principles of noise reduction in a compact, easily assembled structure of large capacity suitable for use with units of large size.

An important principle employed in my improved silencer is that of subdividing or breaking up the initial sound wave into smaller fragments and successively delivering said smaller portions each with reduced energy into the atmosphere so as to practically eliminate all objectionable noise from the unit being silenced. In the practical The annular chambers with their com'muni-- cating ports afford a substantially unrestricted path for the flow of gas and due to their circuitous contour are continually dampening out the energy of the sound are by reflection in addition to the trapping action on the wave and its subdivision into fragments as will be later more particularly explained.

Another. object of the invention is to provide a silencing unit of improved and simplified construction capable of cooperating with duplicate units to alford increased silencing capacity whereby, in a silencer of given dimensions, more or less silencing capacity may be provided by the assembling together of a larger or smaller number of said units.

Further objects of the invention are to provide certain improvements tending to insure strength and rigidity of construction (more particularly in silencers of large sizes such as are required to silence the exhaust noises of large and powerful engines}: to facilitate the economical quantity production of silencers of large capacity: to render practical the construction of large silencers in which provision is made for varying the capacity thereof; and to provide various other improved features of construction contributing to the production of eflicient and reliable silencers at" low manufacturing costs.

To the accomplishment of the above and further objects as will hereinafter appear, the invention consists in the features of construction and in the combinations and arrangements of parts which will first be described and then particularly pointed out in the appended claims.

The invention will be explained with reference to the accompanying drawings, in which Fig. 1 is a view, in longitudinal section, of a silencer, constructed in accordance with the present invention and illustrating what is at present considered to be the preferred form thereof;

Fig. 2 is a sectional view taken along the line 2-2 of Fig. 1.

Referring to the drawings, the improved silencer therein shown comprises a cylindrical casing 1, and a series of silencer units 2 which are assembled side-by-side within the casing 1, adjacent one end thereof.

The casing 1 consists of a tubular shell 3 and disk-like end plates 4 and 5, the latter being secured to the shell 3 by means of bolts 6 which extend throu h marginal portions of the end plates an through out-turned flanges 7 at the opposite ends. of said shell. The end plate 4 is centrally apertured to provide an inlet 8 through which the exhaust gases may enter the silencer, and the end plate 5 is centrally apertured to provide an outlet 9, which is of substantially the same diameter as the inlet 8, and through which the exhaust gases are discharged from the silencer. To enable theexhaust pipe from the engine to be connected with the silencer in such a way as to support the latter rigidly, the end plate 4 is provided with a series of bolt holes 10 that are tapped to receive fastening bolts (not shown) which are adapted to extend also through asuitable tiange on the exhaust pipe. The end plate 5 at the exhaust end of the silencer is similarly provided with a series of bolt holes 152 to facilitate the attachment to the silencer an (not shown) for conveying away the exhaust gases. As shown, an alternative inlet a erture 14 is provided in the side of the she I 3 adjacent the end plate 4. When not in use, the inlet 14 is closed by means of a cover plate 15, the latter being secured to the shell by means of -bolts 16. In case it is found desirable to makause of the inlet 14, the cover plate 15 is removed therefrom and may then be used to cover the inlet-8.

The silencer units 2 are identical and in.- terchangeable except the unit at the innermost end of the series, the latter differing slightly from the rest as will hereinafter appear. With the exception of the innermost one, each unit 2 comprises an annular plate 18 having a plurality of concentric annular flanges or cylindrical walls 19 projecting per endicularly from one face thereof in equa ly spaced-apart relation' from the outer to the inner periphery of said plate. The innermost silencer unit has the same arrangement of concentric flanges 19 as the other units, said flanges projectingfrom a disk like plate 20 which has no axial aperture therein. The plates 18 are somewhat smaller in diameter than the inside of the shell 3. The flanges 19 of each unit, are all of the same width so that the edges at their free extremitieslie in the same plane, parallel to the annular plate 18, or disk 20, as

- plate.

the case may be. Each flange 19 is formed with a cut-away portion forming a port or opening 22, for interconnecting the channels at opposite sides of the flange. The orts 22 in alternate flanges 19 are preferably disposed at opposite sides of the axis of the' silencer, but those at one side of said axis are ofiset from the common diametrical plane of the ports at the other side of said axis for a urpose which will be hereinafter ex plained.

The several silencer units are assembled in coaxial side-by-side relation, as shown in Fig. -1, with the free extremities of the flanges 19 abutting the unflanged faces of the annular plates 18 of the adjacent units, thus closing the open sides of the channels formed between the flanges 19 of the silencer units and converting said channels into a series of concentric annular chambers 23. The assembled units are rigidly and firmly heldtogether by means of tie-bolts 25 which extend axially through the plates 18 at spaced intervals. The tie-bolts 25 also extend through the end plate 5 for the purpose of securing the assembled units 2 to said end Nuts 26 upon the ends of the tiebolts are tightened against the outer face of the end plate 5 to bind the units firmly together. When the units are assembled, as described, the flanges 19'of the several units are alined axially of the silencer and the outermost flanges are spaced a short distance from the inside of the shell 3, thus providing an annular passage 27 aroundthe outer peripheries of the silencer units. To assist in supporting the assembled silencer units and to relieve the tie-bolts 25 of bending strains, a plurality of bolts 28 are threaded radially through the shell 3, in such locations that their inner ends engage suitable hearing faces 29 on one of the units 2, preferably upon the innermost unit, as shown. The bolts 28 can be carefully adjusted to bring the axis of the innermost unit 2 into exact coincidence with the axis of the shell 3 and such adjustment may be permanently maintained by suitable lock-nuts 30 on said bolts.

The size of each port 22 which interconnects adjacent annular chambers 23 is referably at least as large as the cross sectional area of one of the annular chambers; the area of the cross section being taken on a plane passing through the axes of the annular chambers. It is thus seen that the flow of the exhaust gases through the successive thence through the ports 22 in the innermost flanges 19to the alined spaces or chambers 34 at the centers of the silencer units. and thence through the outlet 9 which registers with the chambers 34. It should be noted, however. that the action of the silencer is practically the same in whichever way the gas flows therethrough and conse ilently aperture 9 may be employed as the in et and 10 as the outlet.

As the exhaust gas or other sound wave propagating medium enters the expansion chamber 32 the sound waves expand greatly and as a result the noise energy per unit volume of the gas is greatly reduced. The greater part of the sound waves encounter the flat surface of the disk-like plate 20 of the first silencer unit as they reach the outlet end of the expansion chamber and they are deflected backwardly by this plate and thus trapped within said chamber. of the sound Waves as reach the region adjacent the shell 3 (which is opposite the entrance to the annular chamber 27 are en abled to escape from the expansion chamber 32 into said annular chamber. Since the waves expand outwardly from the axial center of the expansion chamber 32, the noise energy per unit volume of the gas is less in the region adjacent the shell 3 than at' any part nearer the axis of the chamber 32. Thus it will be seen that the entrance to the- Only such mamas passage 27 is located opposite the zone of greatest noise wave expansion and consequently the chamber 32 is made effective to eliminate a maximum amount of the noise.

After reaching the annular passage 27 the sound waves pass, through the port 22 in the outermost'flange 19 into the outermost of the series of annular silencing chambers 23. The stream of gas entering said port 22 is divided by the flanges19 which forms the inner wall of said outermost chamber 23, into two branch streams, as indicated by the arrows a in Fig. 2. the branch streams passing around to the opposite side of the silencer where they are reunited at the port leading into the second chamber 23. As the gas passes into said second chamber it is again divided into two branch streams which flow in opposite directions through the second annular chamber 23 (as indicated by the arrows I) in Fig. 2) until they meet at the opposite side of the chamber, whereupon the reunited streams find an outlet through the adjacent port 22 into the third annular chamber 23. The stream of gas is thereupon again divided into two branch streams and continues to flow back and forth through the interconnected chambers 23 being alternately divided and reunited until it finally reaches the central chamber 34 from which it escapes through the outlet 9.

As the gases progress through the concentric annular chamber 23, the sound waves tend to travel in straight lines and are repeatedly reflected back and forth so that they are broken up and their sound energy is continuously being reduced in the wellknown manner common to many forms of silencers.

In accordance with the present invention however, provision is made for further breaking up the sound waves and insuring the substantially complete elimination of noise from the exhaust. 'To this end the f ports 22 at one side of the silencer are ofiset (ill ing ports 22 at the opposite side of the silencer, thus causing .the branch portionsof a sound wave which occur upon entering one port 22 to each travel a different distance to the next-port 22 and thus remain in sub divided form according to the proper angular spacing'of the successive ports 22.

The amount of the above mentioned offset of the ports 22 is determined relatively to the wave length of the particular sound waves which are to be silenced and is made such as to insure that when thetwo branches of each divided stream of sound wave propagating medium are reunited, the subdivided sound'waves will meet in out of phase relation'. This may be accomplished for sound waves of a certain known wave length by arrangement of the ports 22, asil'lustrated in Fig. 2. Preferablythe ports 22 are alternately arranged on alternate sides of the axis of said silencer and the angular spacing between successive ports is made slightly more or less than 180 so as to insure the out-of-phase relation between said subdivided portions of the sound wave.

The silencing action 1provided by this arrangement may be furt er described as follows. A sound wave entering the port 22 of the outermost annular chamber is there divided, one half going to the right and the other to the left. The half which goes to the left arrives at the next port 22 ahead of that which goes to the right. As each half of the'wave reaches the second port 22, a portion thereof'tails off through said port and is again subdivided in the same manner. The portions of each wave which do not tail off into the second port continue around and around the circuitous chamber in opposite directions and are thereby trapped therein as sound waves pass through one another without the slightest hindrance. However, each time that whichremains of each original half wave passes the port 22, another increment tails off through that port. Every increment that enters the second port goes through thesame procedure in the second-stage channel and so on through the series. In this way, progressive subdivision splits the original wave into an immense number of small fragments which finally enter the atmosphere over an extended period. By the time the leaving wavelet has reached the central exit, it is a very small fraction of the original wave, and of course it is followed by countless succeeding frag-.

ments, coming out one after another. In

addition, the reflections throughout the process effect a further large drop in the noise energy. The final discharge is therefore what amounts to a long, low wave, which is inaudible.

It will be obvious also that the capacity of the silencer will be determined by the number ofsilencer units 2 employed. Thus -amanufacturer, is enabled to readily construct a mufiler of any required capacity by. simply assembling the required number ofv silencer units within the shell 3 and'properly securing them in position. Afterv a Y silencer of this type has been in use its capacity can be readily changed as may be desired by the removal of silencer units from the series or the addition to the series of more units, it being only necessary to employ bolts 25 of the proper length to accommodate the number of units employed. v

It will be seen that the above described silencer is of extremely simple construction and that all the parts thereof may be ad vantageously formed of metallic castings. The silencer units 2- are of such shape that they may be formed economically, each as an integral casting. The ribs 19, as shown,

I mold.

The invention having been described, what is claimed is 1. Ina device of the character described, a structure providing a central chamber surrounded by a plurality of annular chambers of different diameters one outside of the other in series, the circumferential wall of each chamber having a radially directed port at one side only thereof opening directly into the adjacent chamber for unobstructed communication between adjacent chambers, said ports for successive chambers being angularly displaced from one an-. other by more or less than 180 so as to provide in each annular chamber a divided passage of unequal length between successive ports.

2. In a device of the character described, a structure providing a central tubular chamber concentrically surrounded by a group of annular chambers, the circumferential wall of each chamber having a radially directed port at one side only thereof opening directly into the adjacent chamber for unobstructed communication between adjacent chambers, said ports for successive chambers being alternately dis osed at opposite sides of ,the axis of sai angularly displaced from one another 'by more or less than 180 so as to provide in each annular chamber a divided passage of unequal length between successive ports.

3. In a device of the character described, a structure providing a central chamber surrounded by a plurality of annular chambers of different diameters one outside of the other in series, the radial width of each annular chamber being many times smaller than the circumferential length thereof, the circumferential wall of each chamber having a radially directed port at one side only thereof opening directly into the adjacent chamber for unobstructed communication between adjacent chambers, said ports for suca divided passage of unequal length between successive orts.

4. In a evice of the character described,

' a structure providing a central chamber surrounded by a (plurality of annular chambers of different ameters one outside of the other in series, the circumferential wall of each chamber having a port at one side only thereof for communication between adjacent chambers, the size of each port being at least as large as the cross sectional area of an annular chamber, said orts for successive chambers being angulary displaced from one another by more or less than 180 so as to provide in each annular chamber a dithan 180 so as to group and 1,es7,sau

vided passage of unequal length between successive ports.

5. In a device of the character described, a structure comprising a plurality of radially spaced and concentrically arranged cylindrical walls with end closures therefor to provide a series of concentric annular-chambers, each cylindrical wall having a radially directed port at one side only thereof opening directly into the adjacent chamber for unobstructed communication therewith, the ports in adjacent wallsbeing angularly displaced from one another by more or less rovide in each chamber a divided passage 0 unequal length between successive ports.

6. In a device of the character described, a structure comprising a'plurality of radially spaced and concentrically arranged cylindrical walls with end closures therefor to provide a seriesof concentric annular chambers, each cylindrical wall having a port at one side only thereof opening dlrectly'into the adjacent chamber for unobstructed communication therewith, the size of each port being at least as lar e as the cross sectional area of an annular c amber, the ports in adjacent walls being angularly displaced from one another by more or less than 180 so as to provide in each chamber a divided passage of unequal length between successive a structure comprising a plurality of radially spaced and concentrically arranged cylindrical walls, the innermost wall forming a central, tubular chamber and the outer walls a series of concentric annular chambers, end plate closures for said chambers, each cylindrical wall having a radially directed port at one side onl thereof opening directly into the adjacent c amber for unobstructed communication therewith, the ports in adjacent walls being angularly displaced from. one another by more or less than 180 so as to provide in each chamber a divided passage of unequal length between successive ports, an enclosing c lindrical casing for said structure arrange to provide an enlarged expansion chamber at one side of said structure, said casing having its cylindrical wall spaced from the wall of the outermost chamher, one of said end plates closures serving as the endof said cylindrical casing and having an aperture opening into said central tubular chamber.

. 8. In adevice of the class described, a cylindricallcasing having an inlet at one end and a ccntrallya-pertured end plate at its opposite end, a'astructural unit within said casing comprising a plate having a plurality of annular concentric flanges projecting from one side thereof, the outer flange being spaced from said casing and the free ed of said flanges abutting said end plate with III the inner flange registering with the aperture therein to provide a series of annular concentric chambers having a common axis, the adjacent flanges having radially directed ports therein arranged alternatel at opposite sides of said axis and angu arly displaced from one another by more or less than 180 so as to provide in each annular chamher a divided passage of unequal length between successive radially directed ports said ports opening directly into adjacent 0 ambers for unobstructed communication therethrough.

9. In a device of the class described, a cylindrical casing having an inlet at one end and a centrally apertured end plate at its opposite end, a series of structural units within said casing, each comprising a plate having a plurality of annular concentric flanges projecting from one side thereof, theouter flange of each unit being spaced from said casing and the free edges of the flanges abutting the unflanged face of the adjacent unit to provide a series of annular concentric chambers having a common axis, all of said units except the first being centrally apertured with the apertures formed thereby registering with each other and with the aperture in said end plate, openings in the flanges of each unit arranged alternately at opposite sides of said axis and angularly displaced from one another by more or less than 180 so as to provide in each annular chamber a divided passage of unequal length be- Patent No. 1,637,385.

tween successive openings, and means to position said units in said casing and to secure same to said end wall.

10. In a device of the class described, a cylindrical casing having an inlet at one end and a centrally apertured end plate at its opposite end, a series of structural units within said casing, each comprising a plate having a plurality of annular concentric flanges projecting from one side thereof, the outer flange of each unit being spaced from said casing-and the free edges of the flanges abutting the unflanged face of the adjacent unit to provide a series of annular concentric chambers havin a common axis, all of said units except tiie first being centrally apertured with the apertures formed thereby registering with each other and with the aperture insaid end plate, openings in the flanges of each unitarranged alternately at opposite sides of said axis and angularly displaced from one another by more or less than 180 so as to provide in each annular chamber a divided passage of unequal length between successive openings, and means to position said units in said casing and to secure same to said end wall comprising spacing bolts extending through the side walls of said casing and tie bolts extending through said units and said end plate.=

In testimony whereof I have aflixed my signature.

HIRAM PERCY MAXIM.

Certificate of Correction.

Granted August 2, 1927, to

HIRAM PERCY MAXIM.

It is hereby certified that error appears in the printed specification of the abovenumbered patent requiring correction as follows: Page 5,1ines 12 and 13, claim 8, for the word therethrough read therewith; and that the said'Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 6th day of September, D. 1927.

[sun] M. J. MOORE, Acting ammm'seionerof Patents. 

